Typically, vehicle bumpers comprise a primarily plastic and/or steel construction designed for elastic deformation up to a 5 mile per hour impact. These bumpers are typically not of sufficient structural integrity to dissipate substantial energy in a high energy impact, i.e., an impact above 5 mph and up to 40 mph. Accordingly, since such bumper systems are typically 4-6 inches in depth, this 4-6 inches is wasted length which could be used for energy management. Also, such bumpers typically have insufficient structural integrity to generate a deceleration pulse significant enough to be sensed by a vehicle deceleration sensor for airbag deployment.
Another shortcoming of such bumpers is that offset frontal impacts create an energy pulse which is absorbed almost entirely in one of the front rails, and the energy management characteristics of the opposing front rail is not utilized.
Accordingly, it is desirable to provide a bumper and front rail assembly for a vehicle which deforms elastically in a low energy impact (less than 5 miles per hour), and absorbs a greater amount of energy in a high energy or high velocity impact in a manner sufficient to create a deceleration pulse which may be sensed for deployment of an airbag. It is further desirable to create a bumper and front rail assembly for a vehicle in which both front rails are used to dissipate energy in an offset frontal impact.